Connecting means for double needle sewing machines



Aug. 16, 1966 BERG ET AL CONNEC TING MEANS FOR DOUBLE NEEDLE SEWING MACHINES 2 Sheets-Sheet 1 Filed Aug.

Aug. 16, 1966 H. E G ET Al.

CONNECTING MEANS FOR DOUBLE NEEDLE SEWING MACHINES 2 Sheets-Sheet 2 Filed Aug.

XII/f2 1/55:? Wa

United States Patent 3,266,449 CONNECTING MEANS FOR DOUBLE NEEDLE SEWING MACHINES Heinrich Berg and Karl Weber, Kaiserslautern, Germany, assignors to Firm GJVI. Pfatf AG, Kaiserslautern, Pfalz,

Germany Filed Aug. 31, 1965, Ser. No. 483,944 Claims priority, application Germany, Oct. 2, 1964, P 35,203 6 Claims. (Cl. 112221) The invention relates to control means for the needle bars of sewing machines. In particular, the invention is concerned with a device provided on double needle sewing machines for optionally connecting and disconnecting the needle bars, which are arranged directly alongside one another in a needle bar oscillator frame and which are slidably guided in a carrier sleeve encompassing both needle bars and provided with coupling means for the needle bars and for effecting the drive of the needle bars. In this environment the needle bars are carried along by the carrier sleeve to the upper dead point position after having been disconnected. In that position their upper ends rest against a cushioning spring.

In known arrangements of this type each needle bar is uncoupled separately in that a manually operable wedge member is placed between the needle bar drive member and the head of a coupling bolt which is spring biased and adapted to couple the same with the needle bar For connecting an uncoupled needle bar a device is provided which is manually operable and which simultaneously acts on both needle bars and which is installed at the top of the sewing machine head. As a result the entire mechanism cannot be used for Zig-zag sewing machines. Besides, such embodiments can only be installed in machines having a relatively low number of rotations and where the distance between the needles is relatively large. That is because for safe coupling the coupling bolt which is spring biased must interengage the needle bar relatively deeply in a bore provided therein. Furthermore, a certain space is required between the two coupling bolts for accommodating them and for the arrangement of return springs.

It is an object of the invention to simplify the known arrangements while simultaneously improving their operational safety and thus decrease costs, and to make possible the installation in double needle straight stitch and zig-zag sewing machines also of the compound and needle transport type while eliminating expensive conversion and adjusting operations. Accordingly the invention is based on the technical problem of constructing the needle bar drive, particularly its coupling means for the needle bars, in such a manner that the needle bars may be rapidly and reliably connected and disconnected at high sewing velocities while avoiding exact.

alignment of the coupling elements prior to coupling and while foregoing the close tolerances in manufacture that were necessary heretofore, and to arrange the shifting means proper in such a manner that while shortening the shifting paths it constitutes a pre-assembly unit with the needle bar mechanism. In accordance with the invention this problem is solved in that two tilting levers which are spring biased and pivotally secured to the carrier, whose one end is in the form of pawls or carrier hooks for the needle bars and whose other end cooperates with a pressure surface on a shifting bar for rocking the tilting levers and which is mounted in the oscillator frame parallel at a distance with respect to the needle bars.

A particularly advantageous form of construction of the switching device with the needle bars connected and disconnected individually and together is obtained in that the shifting bar is constructed in two parts.

Patented August 16, 1966 Each needle bar is thus associated with its own shifting bar portion so that it can be connected and disconnected independently of the other.

A wedging of the two shifting bar parts is avoided while simultaneously improving the ease of operation by means of a roller member whose axis of rotation coincides with the common axis of rotation of the parts.

For arresting the two needle bars in their upper dead point position known safety elements may be utilized. However, it is advantageous if the shifting bar has one catch spring for each of the two needle bars provided with catch grooves in their upper dead point position at the level of the catch springs, and a switching arm for a cushioning spring secured to the oscillator frame, which cooperates with a movable supporting spring that is likewise fastened to the oscillator frame and is movable by means of the switching arm into a supporting and release position, where the supporting of the cushioning spring is effected in the connecting position of the needle bars above the path of operation of the needle bars.

In this manner the cushioning spring required as a brake for the needle bars performs a double function. In the first place the early release causes a braking force to be applied to the needle bars and thus to improve the braking effect. In the second place the supporting of the cushioning spring above the path of operation of the needle bars by means of the supporting spring during the normal operation of the machine prevents knocking of the needle bars against the cushioning spring. In practical operation this measure operates in a manner that with relatively high numbers of rotation it is possible to connect and disconnect and to avoid completely the contact noises of the needle bars at the cushioning spring.

A particularly simple and economical embodiment of the mechanism for simultaneously connecting and disconnecting the two needle bars, the operation of which requires almost no attention during sewing and which enables the seamstress to undertake the disconnecting of the needle bars without taking her attention from the work, is obtained by a switching bar pivotally mounted on the oscillator frame and having two longitudinal ribs for shifting the tilting levers and a locking slide which is spring biased which with the switching ,bar in operative position interengages the grooves in the needle bars in the upper dead point position.

Further advantageous features and objects of the invention will become apparent with reference to the embodimen'ts illustrated by way of example in the accompanying drawings, in which FIG. 1 is a perspective illustration of the mechanism showing the sewing tools in the head of the sewing machine with the left needle bar-disconnected,

FIG. 2 is a perspective view of the cushioning arrangement for the needle bar,

FIG. 3 is an illustration similar to FIG. 1 in which the shifting bar for the needle bars is constructed in two parts and where both needle bars are connected for operation.

. FIG. 4 is a section taken along the line IVIV in FIG. 3, drawn to an enlarged scale,

FIG. 5 is a section taken along the line VV in FIG. 3, drawn to an enlarged scale, where one component part of the shifting bar illustrated in FIG. 3 is shown in the disconnected position for the left needle bar, and

FIG. 6 shows a section taken along line VI-VI of FIG. 3, drawn to an enlarged scale.

The arm shaft 1 of the sewing machine imparts reciprocating movements to the carrier sleeve by way of the arm crank 2 and the needle bar link 3. The carrier sleeve 4 has two bearing lugs 5, 6 between which two tilting levers 8, 9 are pivotally secured by means of a .pin 7. Each of the two tilting levers 8, 9 is provide dat one end with a configuration constituting a pawl 10, and at the other end it has a laterally extending offset 11. The tilting levers 8, 9 are each biased by a spring 12 arranged between the carrier sleeve 4 and the end of the lever at which the offset 11 is provided.

The left and the right needle 'bars 13, 14, respectively, are slidably guided in the carrier sleeve 4, each having a transverse member 15 provided with a shoulder 16 for the pawls 10 of the tilting levers 8 and 9. If both needle bars 13 and 14 are connected for operation, then the pawls 10 are in engagement with the shoulders 16. The two needle bars 13, 14 whose cross sections complement each other to constitute a circular plane (see FIG. 4) are in addition carried in a needle bar oscillator frame 18 of the machine with the rocking shaft 17 to impart reciprocating movement thereto.

For better guidance the carrier sleeve 4 has a stud (not shown) at the side away from the tilting levers 8, 9, which has an end which projects from the needle bar link 3 where a sliding block 19 is arranged. The sliding block 19 is guided in a guide slot 20 arranged in the oscillator frame 18.

A shifting bar 21 is rotatably journalled in the needle bar oscillator frame 18 at a distance from and parallel with respect to the needle bars 13, 14. The shifting bar 21 has a setting lever 22 at its lower end which is secured in a collar 23 of the shifting bar 21. A pressure spring 24 is provided at the shifting bar 21 between the collar 23 and the lower side of the needle bar oscillator frame 18 by means of which the shifting bar 21 together with the setting lever 22 is pressed downwardly into a position where the setting lever 22 engage one of the three grooves 25 which determine the three operating positions. The grooves 25 are provided in a supporting block 26 secured to the needle bar oscillator frame 18, which block is provided with indicating marks. The setting positions of the scale L, O, R indicate:

L left needle bar disconnected 0 both needle bars connected R right needle bar disconnected Along the range of operation of the offsets 11 the shifting bar 21 is in the form of a three-cornered prism having a base .plane defining an are on a triangle, the even lateral surfaces of which constitute pressure surfaces 27, 28 for the offsets 11 to permit tilting of the tilting levers 8, 9.

' At the upper end of the shifting bar 21 a catch spring 29 having spread apart arms 30, 31 is secured. The needle bars 13, 14 each have a catch groove or recess 32, 33 which are somewhat wider than the arms 30, 31 of the catch spring 29. At the upper dead .point of the needle bars 13, 14 the upper edges of the grooves 32, 33 and the upper edges of the arms 30, 31 are disposed at the same level.

In order to provide for soft, substantially silent and largely shock-free connecting and disconnecting of the needle bars a cushioning spring 34 is secured to the needle bar oscillator frame 18 by means of screws 35 which permit adjustment to the proper level and which spring carries at its angularly offset arm above needle bars 13, '14 an elastic abutment 36. The outer end of the bottom side of the arm carrying the abutment 36 of the cushioning spring 34 is slightly beveled. At the surface of the needle bar oscillator frame 18 which is remote from the mounting surface for cushioning spring 34 a support spring 37, which is likewise adjustable to the proper height, is secured which is movable by means of a cam 38 defined at the upper end of the shifting bar 21, which cam is in the form of a shifting arm from a position in which it extends under and supports the cushioning spring 34 at the arm which carries the abutment 36, and which is movable against its own spring force, into a position in which the cushioning spring 34 is freed, so that its angularly offset arm with the abutment 36 is released toward the upper ends of the needle bars. The supporting of the cushioning spring 34 by the support spring 37 is effected at the arm of the spring 34 which carries the elastic abutment 36 at a level at which the lower side of the abutment 36 is located somewhat above the path of movement of the needle bars 13, 14. In this manner the needle bars when connected will not touch the abutment 36 during the operation of the machine.

In the supporting block 26 a switching bar 40 is pivotally supported by means of a bolt 39 against the pressure of a spring 41. The spring 41 is slid over a limiting screw 42 secured in the needle bar oscillator frame 18 and extends between the inside of the switching bar 40' and the needle bar oscillator frame 18.

The switching bar 40 has an upper portion 43 which is angularly offset with respect to the needle bars 13. In a recess 44 of the upper part 43 a locking slide 45 is slidably accommodated which is under the effect of a spring 47 arranged about a limiting screw 46 in the recess 44. In the upper dead point position of the two needle bars 13, 14 the locking slide 45 engages the catch grooves 48, 49 of the needle bars 13, 14 when the switch bar 40 i angularly moved with respect to the needle bars 13, 14.

In order to rock the tilting levers 8, 9 the switch bar 40 has two parallel longitudinal ribs 50 at the side facing the needle bars 13, 14, which ribs are arranged at a distance from one another which is somewhat greater than the diameter of the shifting bar 21. The surfaces of the longitudinal ribs which face the needle bars 13, 14 define pressure surfaces 51 for the offset members of the tilting levers 8, 9 and extend over the entire length of the path of movement of the offsets 11 of the levers 8, 9.

It must also be mentioned that the switching bar 40 is arranged within a section 52 of the head plate 53 of the machine and in order to release the cushioning spring 34 when both needle bars are disconnected is provided with a projection 54 having an inclined surface 55 (FIG. 2) for moving the support spring 37 outwardly.

It can be seen that all par-ts of the needle bar device with its disconnecting mechanism are removable as a unitary assembly by means of the rocking shaft 17 after the head plate is removed, so that the preassembled unit can also be installed in straight stich and zig-Zag sewing machines of the type which are provided with compound feed.

The manner of operation of the arrangement thus for described will be explained hereinafter with reference to the example of the switching operation as the left needle bar 13 is disconnected and connected. In this connection it is assumed that both needle bars are connected, for which purpose the pivotable lever 22 is disposed in the center position 0.

If the pivotal lever 22 is moved from its center position 0 to the position L, then the shifting bar 21 rotates first into a position where the pressure surface 27 reaches the path of movement of the offset 11 of the left needle bar 13 with the tilting lever 9 coupling the carrier sleeve 4. During the further course of the rotary movement the tilting lever 9 is pivotally moved by the pressure surface 27 against the effect to the spring '12, whereby the pawl 10 of the tilting lever 9 releases the shoulder 16 of the transverse member '15 of the needle bar 13.

While turning the shifting bar 21 the double armed catch spring 29 and the shifting cam 38 are simultaneously carried along in the direction of rotation. The arm 30 of the spring 29 is pressed against the needle bar 13 against its own resiliency. At the same time the support of the cushioning spring 34 is eliminated by bending of the support spring 37 outwardly by means of the shifting cam 38, and the cushioning spring 34 is released so that its upper arm approaches the needle bars 13, 14. During the upward movement of the carrier sleeve 4 the needle bar 13 is carried along to its upper dead point position where it is retarded very soon by the cushioning spring 34. In the upper dead point position of the needle bar the arm 30 of the catch spring 29 engages the catch groove 32 of the needle bar 13. The left needle bar is thus held in its uppermost position and does not take part in the further sewing operation. Owing to the retarding effect of the cushioning spring 34 which starts very early, and the somewhat greater width of the catch groove 32 with respect to the width of the arm 30, the disconnect-ing or switching operation can also be undertaken at a relatively high number of rotations of the machine.

For reengaging the left needle bar 13 the shifting bar 21 is turned by means of the shifting lever 22 into its initial position (center position 0 of the shifting lever 22). In this connection the pressure surface 27 frees the offset 11 of the tilting lever 9 which is under the effect of the spring 12, and the shifting cam 38 frees the supporting spring 37 which is under its own spring tension; the arm 30 of the catch spring 29 disengages the catch groove 32 and frees the needle bar 13, which thereupon is pressed downwardly under the effect of the cushion spring 34 with its transverse member 15 against the upwardly moved carrier sleeve 4, so that the pawl of the tilting lever 9 can engage the shoulder 16. Thus the needle bar 13 is connected or engaged. In the upper dead point position of the needle bar 13 the support spring 37 projects under the cushioning spring 34 and supports it due to the inclination at the outermost edge of the lower side of the arm carrying the abutment 36, at a level at which the needle bar does not touch the abutment 36 from below when the machine is running.

The manner of operation of the arrangement for connecting and disconnecting the right needle bar 14 is substantially the same as described above, so that any explanation in this respect is unnecessary.

If the needle bars 13, 14 are to be simultaneously disconnected, the switch bar 40 is moved manually against the force of the spring 41 in the direction of the needle bars 13, 14 about the bolt 39, so that first the support spring 37 is turned outwardly by means of the projection 54 that is provided with the bevelled surface 55, and thus the cushioning spring 34 is freed. The sliding block 45 which is under the effect of the spring 47 is then pressed against the needle bars 13, 14. Simultaneously the pressure surfaces 51 of the longitudinal ribs 50 contact the ofisets 11 of the tilting levers 8, 9, and the levers 8, 9 are moved against the pressure of the springs 12 so that the pawls or hooks 10 release the shoulders .16. The needle bars 13, 14 thus disengaged are carried along against the force of the cushioning spring 34 that has been released by the supporting spring 37 until they reach their upper dead point posit-ion in which the catch grooves 48, 49 arrive at the same level as the sliding block 45 that is pressed against the needle bars 13, 14. The sliding block or lock 45 is pressed by spring 47 into the catch grooves 48, 49, so that the disengaged needle bars are held in their highest position until the switch bar 40 is released, which thereupon returns into position of rest under the effect of spring 41. Thus the supporting spring 37 and the offsets 11 of the tilting levers =8, 9 are again released.

The reengaging of the needle bars is effected in the same manner as described above in connection with the reengaging of the left needle bar 13.

FIGS. 3 to 6 illustrate an improved and simultaneously modified embodiment of the switching device where the shifting bar 121 consists of two parts 156, 157. The construction of the shifting bar in two parts makes it possible, while eliminating the shifting bar 40 to optionally engage and disengage the needle bars .113, 114 separately or together.

The partial members 156, 157 of the shifting bar 12 1 have an upper section 158 or 159 of arcua-te triangle cross section (see FIG. 4) which extends partly into the needle bar oscillator frame 118 and a central section 160 or 161 of rectangular cross section (see FIG. 5). As

shown in FIG. 5, the edges of the center section 160, 161 of the two components parts 156, 157 which face the needle bars 1'13, 114 are flattened away from the axis of rotation. The surfaces thus formed constitute pressure surfaces 162, 163 for theoffsets 11 of the tilting levers 8, 9 which extend over the entire range of movement of the offsets 11 of the levers 8, 9.

At the lower end of the component part 157 the needle bar oscillator 118 has arranged therein a sleeve 164 in which the cylindrical lower end 165 of the component part 157 of the shifting bar is rotatably received. The sleeve 164 is rigidly connected with the sections 158, 160, for example, by hard soldering. The two component parts 156, 157 of the shifting bar 121 are rotatable about a common axis. In order to improve the ease of movement of the shifting bar 121 a rolling body 166 (FIG. 4) is arranged in the needle bar oscillator frame 118 between the two component parts 156,157 in corresponding grooves in the region of the upper bearing support of the sections 158, 159 of the parts 156, 157, the axis of rotation of which rolling body coincides with the common axis of rotation of the components 156, 157 of the shifting bar 121.

On both sides of the axis of rotation of the rocking shaft 17 of the machine and at equal distances therefrom a shifting lever 167, 168 is secured in the components 156, 157. The shifting levers 167, 168 project outwardly through a slot 169 (only one slot is shown) in the head cover 153. The slots 169 are so constructed that the shifting levers 167, 168 can be turned from their center position shown in FIG. 3 only in opposite directions and outwardly. In this manner faulty witching is avoided.

At the upper bearing support of the needle bar oscillator 118 the outwardly extending ends of the components parts 156, 157 of the shifting bar 121 are each provided with a catch spring 170, 171 and a pressure bar 172, 173. In the uppermost position of the needle bars 113, 114 the catch springs 170, 171 engage catch grooves 132, 133, respectively, when the partial components 156, 157 of the shifting bar 121 are in their disengaged position and re tain the needle bars 113, 114 in the uppermost position.

The pressure bars 172, 173 serve for bending or turning the support spring 37 when the components 156, 157 are rotated.

For securing the components 156, 157 of the shifting bar 121 in their positions of operation the sleeve 164 is provided with a flange 174 constructed in the form of a catch disk and having two grooves 175, 176. At the lower end of the component 157 there is likewise provided a catch disk 179 provided with grooves 177, 178 which are secured against turning .by lateral flat surfaces 180 (FIG. 6) at the lower end of the component 157 and by a corresponding longitudinal slot in the catch disk 179.

A projection 181 of the oscillator frame 118 is provided with bores (not shown) where-two balls 182 which are spring biased (not shown) engage the corresponding grooves 178 in the catch disks 174, 179 when the components 156, 157 are in operative position.

The securing in axial. position of the shifting bar 121 is effected at the upper end of the needle bar oscillator 118 by a split ring 183 and at the lower end by a disk (not shown) secured by means of screw 184 to the component 157.

Since the manner of operation of the device last described is the same for both needle bars and compares to the manner of operation of the device having the shifting bar in the form of a unitary structure described hereinabove, the manner of operation of the last described device during the disconnecting of the left needle bar 113 is only briefly explained. The starting position is assumed to be the position of the parts shown in FIG. 3, where both needle bars are connected and where the shifting levers 167, 168 rigidly connected with the components 156, 157 are in their central position.

If the shifting lever 167 is turned from its center position to the position shown in FIG. 5, then the component part 156 of the shifting bar 121 in the sleeve 164 and in the upper bearing support in the oscillator frame 118 turns about the common axis of rotation of the two component parts 156, 157. By means of the pressure surface 162 (FIG. cooperating with the offset 11 of the tilting lever 9 the tilting lever 9 is turned against the force of the spring 12 and the pawl of the tilting lever 9 releases the shoulder 16 of the needle bar 113. Simultaneously with the turning of the component 156 the supporting spring 37 is turned outwardly by way of pressure strip 172, and the catch spring 170 is pressed against the needle bar 113 counter to its own resiliency. By turning the supporting spring 37 the cushion spring 34 is released, whose arm which is provided with the abutment 36 approaches the upper ends of the needle bars as the cushioning spring 34 is relaxed. In the disconnected position the component 156 is fixed by the ball 182 which engages the groove 176 of the flange 174.

During the upward movement of the carrier sleeve 4 the needle bar 113 is carried along to its highest position counter to the effect of the cushioning spring 34, where the catch spring 170' enters the catch groove 132 of the needle bar 113, and the needle bar 113 is held in this position where it does not participate in the sewing operation until the component 156 of the shifting bar 121 is shifted back to the center position by means of the shifting lever 167.

As a result the pressure surface 162 at the center section 160 of the component 156 releases the tilting lever 9 and the pressure strip 172 frees the supporting spring 37.

Due to the engagement of the pawl 10 of the tilting lever 9 with the shoulder 16 under the action of the spring 12 the needle bar 113 is again connected. In the highest position of the needle bars the supporting spring 37 projects under the arm of the cushioning spring 34 which is provided with the abutment 36 and supports spring 34 by virtue of the slight incline at the outer end of the lower side of the arm which carries the abutment 36 somewhat above the upper dead point of the needle bars 113, 114. The upper endsof the needle bars 113, 114 therefore do not engage the abutment 36 during the operation of the machine.

Having now described our invention with reference to the embodiments illustrated in the drawings, we do not wish to be limited thereto, but what we desire to protect by Letters Patent of the United States is set forth in the appended claims.

We claim:

1. Device for optionally connecting and disconnecting the needle bars in a double needle sewing machine of the type having a drive shaft and a rocking shaft, a needle bar oscillator operatively connected to said rocking shaft and a pair of needle bars arranged adjacent to one another, a member on each said needle bar presenting a shoulder, and a retaining configuration on each needle bar for holding the bar in inoperative position, a carrier sleeve slidingly supporting said needle bars in said needle bar oscillator and operatively connected to said drive shaft, coupling means provided on said carrier sleeve for selectively coupling said needle bars to said sleeve comprising a pair of spring biased tilting levers pivotally supported on said sleeve, each lever having a pawl at one end for engagement with one said shoulder and having an offset member at the other end, a shifting bar device rotatably supported on said oscillator sleeve presenting a pair of pressure surfaces generally parallel to said carrier, one for each said offset, manual means for angularly moving said shifting bar device and thereby one said tilting lever to disengage one said shoulder, a pair of spring arms carried at the upper end of said shifting bar device and angularly movable therewith for engagement of one said spring arm with one said retaining configuration in the upper dead point position of the associated needle bar.

2. Device in accordance with claim 1, comprising a cushioning spring carried by said needle bar oscillator proximate the upper end of said needle bars for engagement by a needle bar in inoperative position.

3. Device in accordance with claim 2, comprising a support spring operatively associated with said cushioning spring, a cam member operative to move said support spring, mounted on said shifting bar device and movable thereby to support said cushioning spring above the upper ends of said needle bars when said needle bars are in operative positions.

4. Device in accordance with claim 2, where said shifting bar is formed in two component parts.

5. Device in accordance with claim 4, where said component parts define grooves and a roller member is disposed in said grooves, said roller member being movable with said components about a common axis of rotation.

6. Device in accordance with claim 1, comprising a switch bar pivotally mounted at the lower end of said needle bar oscillator and having a pair of longitudinal ribs proximate said offsets operative to move said tilting levers outof engagement with said shoulders, a spring biased locking slide carried in the upper end of said switch bar, and a catch groove in each said needle bars for engagement by said locking slide when said needle bars are in the upper dead point position.

References Cited by the Examiner UNITED STATES PATENTS 1,243,921 10/1917 Corr-all 112221 1,386,323 8/1921 De Voe 112-221 1,695,680 12/1928 Card 112-221 1,754,608 4/1930' Card 11222l 2,868,152 1/1959 Benink et al. 11222l 3,058,436 10/1962 Goosman 11222l FRANK J. COHEN, Primary Examiner. 

1. DEVICE FOR OPTIONALLY CONNECTING AND DISCONNECTING THE NEEDLE BARS IN A DOUBLE NEEDLE SEWING MACHINE OF THE TYPE HAVING A DRIVE SHAFT AND A ROCKING SHAFT, A NEEDLE BAR OSCILLATOR OPERATIVELY CONNECTED TO SAID ROCKING SHAFT AND A PAIR OF NEEDLE BARS ARRANGED ADJACENT TO ONE ANOTHER, A MEMBER ON EACH SAID NEEDLE BAR PRESENTING A SHOULDER, AND A RETAINING CONFIGURATION ON EACH NEEDLE BAR FOR HOLDING THE BAR IN INOPERATIVE POSITION, A CARRIER SLEEVE SLIDINGLY SUPPORTING SAID NEEDLE BARS IN SAID NEEDLE BAR OSCILLATOR AND OPERATIVELY CONNECTED TO SAID DRIVE SHAFT, COUPLING MEANS PROVIDED ON SAID CARRIER SLEEVE FOR SELECTIVELY COUPLING SAID NEEDLE BARS TO SAID SLEEVE COMPRISING A PAIR OF SPRING BIASED TILTING LEVERS PIVOTALLY SUPPORTED ON SAID SLEEVE, EACH LEVER HAVING A PAWL AT ONE END FOR ENGAGEMENT WITH ONE SAID SHOULDER AND HAVING AN OFFSET MEMBER AT THE OTHER END, A SHIFTING BAR DEVICE ROTATABLY SUPPORTED ON SAID OSCILLATOR SLEEVE PRESENTING A PAIR OF PRESSURE SURFACES GENERALLY PARALLEL TO SAID CARRIER, ONE FOR EACH SAID OFFSET, MANUAL MEANS FOR ANGULARLY MOVING SAID SHIFTING BAR DEVICE AND THEREBY ONE SAID TILTING LEVER TO DISENGAGE ONE SAID SHOULDER, A PAIR OF SPRING ARMS CARRIED AT THE UPPER END OF SAID SHIFTING BAR DEVICE AND ANGULARLY MOVABLE THEREWITH FOR ENGAGEMENT OF ONE SAID SPRING ARM WITH ONE SAID RETAINING CONFIGURATION IN THE UPPER DEAD POINT POSITION OF THE ASSOCIATED NEEDLE BAR. 